RIOFH - Repository of Institute of General and Physical Chemistry
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Reduction of hexavalent chromium by Bacillus spp. isolated from heavy metal-polluted soil [Redukcija šestovalentnog hroma pomoću Bacillus spp. izolovanih iz zemljišta kontaminiranih teškim metalima]
No full textHexavalent chromium, Cr(VI), one of the major pollutants from industrial facilities, is very toxic and harmful for human health and environmental quality. Due to the lack of conventional methods, bioremediation was recommended as an environmentally friendly and effective technique. The aim of this paper was the isolation, identification and selection of the microorganisms which are capable of Cr(VI) reduction in vitro. Heavy metal concentration, detected in four soil samples, within and around the former bicycle factory “Rog” (Republic of Slovenia), was measured using the ICP-OES method. Bacteria were isolated and tested for chromium tolerance using LB agar supplemented with various Cr(VI) concentrations, whilst Cr(VI) reduction and bacterial growth was determined using the LB liquid medium. From 53 bacterial isolates, five of them showed a tolerance of 1000 mg/L of Cr(VI). Those five isolates showed the capability of growth under various Cr(VI) concentrations (50-1000 mg/L). Initial Cr(VI) concentrations ranging from 50 to 100 mg/L were completely reduced by four bacterial isolates, whilst 500 to 1000 mg/L by Bacillus safensis 342-9. Using 16S rDNA and tuf gene sequence analyses, isolates 270-9R and 342-9 were identified as Bacillus safensis, isolates 351-9 and 270-9C as Bacillus subtilis subsp. subtilis, and 212-9 as Bacillus thuringiensis. These results indicated that these bacteria may be promising tools for remediation of metal-polluted sites
Micellization and Foamability of Sodium Laureth Sulfate and Polysorbate Surfactant Mixtures
No full textThe micellization behavior and foamability of a mixture of anionic surfactant sodium laureth sulfate (SLES) and nonionic polysorbate surfactants commercially available as Tween series were investigated. The mole fraction and the structure of the hydrophobic part of various polysorbates affect the critical micellar concentration (CMC) and foam height and stability of anionic surfactant. Experimental values of CMC were determined by measuring specific conductivity at 25 degrees C and foam height and stability by modified RossMiles method at 23 degrees C. The negative deviation of the experimentally determined CMC from theoretical values for ideal mixed micelle indicate non-ideal mixing behavior due to synergism as a consequence of attractive interactions between the individual surfactants in formed micelles. Thus synergism increase with increasing of both the mole fraction and length of hydrophobic tail of examined Tween in SLES/Tween mixtures. Foam height and stability significantly decrease with increasing length of the hydrophobic tail of Tween surfactants and their mole fractions in the binary mixture
Shelf life and quality of dehydrated meat packed in edible coating under modified atmosphere
No full textEffects of modified atmosphere packaging, with the addition of an active edible coating on quality and shelf-life of osmotically dehydrated pork meat was investigated. The pork was osmotically dehydrated, coated with starch based active edible coating with oregano essential oil and packed under atmospheric conditions and under modified atmosphere. The packaged meat was kept at 4 degrees C for 2 months and was analyzed physico-chemically, microbiologically and sensorially. All physico-chemically parameters were improved and shelf-life was prolonged. Meat quality was promoted by using modified atmosphere packaging with active edible coating.Lipid oxidative changes were less pronounced in samples packed under modified atmosphere. The microbiological profile showed that the osmotic dehydration is hygienically safe, but samples packed under modified atmosphere showed higher level of microbial stability compared to samples packed in atmospheric conditions, although all groups remained stable during 60 days (which is a result of the active edible coating application)
Physicochemical Changes of the Gluten-Free Rice-Buckwheat Cookies during Storage - Artificial Neural Network Model
No full textThe influence of storage time, temperature, and packaging on some physicochemical characteristics of gluten-free rice-buckwheat cookies was studied. Shelf life markers, such as water activity (a(w)), hydroxymethylfurfural (HMF), firmness, and color parameters were modelled in relation to different storage conditions. Principal component analysis was applied to study the similarity among samples according to the observed parameters. The mathematical model in the form of an artificial neural network was developed to predict the physicochemical parameters of cookies during 6-month storage. The most evident differentiation among samples was observed for color coordinate a*, a(w), and HMF. Regarding the methods for determination of the parameters, priority should be given to the instrumental determination of color as the most convenient method. The processing of experimental data allowed the creation of useful mathematical model to be used in predicting the behavior of physicochemical changes of cookies by different factor combinations during storage
Survival of Wild Strains of Lactobacilli During Kombucha Fermentation and Their Contribution to Functional Characteristics of Beverage
No full textKombucha is a fermented tea beverage, which is traditionally prepared by fermenting sweetened black tea with tea fungus, which is a consortium of yeasts and acetic acid bacteria. In this paper, viability of selected wild strains of lactobacilli during Kombucha fermentation, their interaction with tea fungus and their contribution in obtaining a beverage of increased functional characteristics were tested. Five wild strains which were isolated from traditionally fermented foods were separately added on the second day of Kombucha fermentation. Count of yeasts, acetic acid bacteria and lactobacilli, as well as pH, titratable acidity, and content of L- and D-lactic acid during Kombucha fermentation were determined. Wild strains of lactobacilli demonstrated a differentiated survivability and the counts in fermentation broth (i.e. Kombucha beverages) depending on the strain applied. The addition of wild Lactobacillus spp. during Kombucha fermentation had no effect on the physiological activity of tea fungus, but they contributed to a significant increase in lactic acid content in the beverage. The highest lactic acid content during Kombucha fermentation was produced by the strain of Lactobacillus plantarum isolated from 40-day-old cream, while the strain of Lactobacillus hilgardii (from sour dough) showed the highest viability
Vibrational Quenching in Near-Infrared Emitting Lanthanide Complexes: A Quantitative Experimental Study and Novel Insights
No full textTwo series of novel NIR-emissive complexes of Nd3+, Sm3+, Er3+ and Yb3+ with two different beta-diketonate ligands (L-1=4,4,4-trifluoro-1-phenyl-1,3-butadione and L-2=4,4,4-trifluoro-1-(4-chlorophenyl)-1,3-butadione) are reported. The neutral triphenylphosphine oxide (tppo) ligand was used to replace coordinated water molecules in the first coordination sphere of the as-obtained [Ln(L-1(2))(3)(H2O)(2)] complexes to afford water-free [Ln(L-1(2))(3)(tppo)(2)] molecular species. Upon replacement of water molecules by tppo units, the NIR emission lifetimes of the Nd3+, Er(3+)and Sm(3+)complexes increase by about one order of magnitude up to values of approximate to 9, 8 and 113 ms while Yb3+ complexes reach intrinsic quantum yields as high as to phi(Yb)=6.5 %., which are remarkably high for fully hydrogenated complexes. Vibrational quenching by CH and OH oscillators has been quantitatively assessed by implementing the Forster's model of resonance energy transfer on the basis of experimental data. This study demonstrates that highly efficient NIR-emitting lanthanide complexes can be obtained with facile, cheap and accessible syntheses through a rational design
Assessment of the effectiveness of producing mineral fillers via pulverization for ceramic coating materials
No full textThe effectiveness of employment of mechano-chemical activation in the production of high temperature ceramic coating materials was assessed. The properties of mineral fillers are directly dependant on the choice of activation variables. Mathematical modeling was employed for optimization of ultra-centrifugal pulverization and determination of optimal characteristics of investigated materials. The properties of treated resources were mathematically correlated to the variations in their granulometry. The dependencies between the set of the activation parameters and characteristics of a material were mathematically modeled and estimated. Chemometric methods were employed in the calculations. The samples are classified by Principal Component Analysis, while comprehensive comparison between analyzed samples was achieved by Response Surface Method and Standard Score. Mathematical models predict the quality parameters of activated powders with high accuracy in a broad range of processing parameters. The r2 values were in the range from 0.71 to 0.98 for established models for processing of talc, mica, fly ash and alumina powders. The set of processing parameters related to the 120 Μm sieve mesh size was selected as optimal procedure with acquired standard score values 0.7 for mica, 1.0 for talc, 0.9 for fly ash and alumina. Optimal processing parameters can diminish the negative effect of raw materials inherent properties on the target score, which in return enhances energetic and economic sustainability of the mechano-chemical activation of resource materials utilized in the production of ceramic coating materials
The variation of mineral content in celery root during the treatment in two osmotic solution
No full textIn this study, the changes in the content of potassium, magnesium, calcium and iron of celery root during osmotic treatment were evaluated and compared for different process conditions. The main objective was to investigate the possibility of enhancing the mineral content of treated material using sugar beet molasses as osmotic medium. Celery (Apium graveolens) has been known as a traditional medicinal plant or spice, and as an excellent source of minerals is vital for the maintenance of human health. During conventional drying of celery, high temperature and the presence of oxygen, can negatively affect the composition of the minerals. In order to preserve health benefits substances, osmotic treatment which involves immersion of the raw material in concentrated solutions on the mild temperatures, has been suggested. Osmotic treatment implies three simultaneous flows: migration of water from the submerged material into the surrounding solution, penetration of dissolved substances from the solution into the plant tissue and leaching out of the tissue`s own solutes. Due to the rich nutrient and mineral composition, molasses as osmotic solution might contribute an improvement to the nutritive quality of the treated products. Osmotic treatment of celery root in two osmotic solutions (mixture of sucrose and sodium chloride aqueous solution and sugar beet molasses), at three temperatures (20, 35 and 500C), and immersion periods (1, 3 and 5 h) was performed. The influence of used osmotic agent, temperature and immersion time of the change of mineral content of the samples was investigated. The content of analyzed mineral matters in fresh and treated samples was determined by atomic absorption spectro-photometer according to the standard methods. The results revealed observable improvement of the mineral content of celery root treated in molasses, while the samples treated with sucrose and sodium chloride solution showed reduction of the examined mineral matters. After 5 h of osmotic treatment in molasses, on the 500C, the content of minerals in samples (mg/100 g) was increased: for K from initial 365.85 to final 766.52; for Mg from 22.42 to 36.98, for Ca from 44.12 to 57.36 and for Fe from 0.76 to 0.91. It can be concluded that molasses due to the rich mineral composition contributes to improving the nutritive quality of the treated products
Application of soybean oil and glycerol in animal feed production, ANN model
No full textIn the past few decades the diet preparation in feed production has evolved towards more complicated technological operations, which include different liquid addition. A wide scale of different liquids is used in contemporary animal feed production, from oils and glycerol to more expensive products in a liquid form, such as enzymes, flavourings, amino acids, vitamins and others. In the presented study the liquid addition in feed production was observed, with a specific goal to investigate the spraying systems in order to better understand the effects of fluids, such as soybean oil and glycerol, on feed production. The dispersion angles of spraying nozzle for glycerol and soybean oil were determined as an indicator of the uniform application of liquids during feed production. Dispersion of the material was accomplished using the two-fluid nozzle. The performance of Artificial Neural Network (ANN) was compared with experimental data in order to develop rapid and accurate method for prediction of dispersion angle. The ANN model showed high prediction accuracy (r2 = 0.945)
Ionization Energies of LinCln – 1 (n = 3, 4, and 5) Clusters Studied by the Modified Knudsen Cell Mass Spectrometry Method
No full textAbstract: In the present paper, ionization energies of LinCln – 1 (n = 3, 4, and 5) clusters were studied by means of the modified Knudsen cell mass spectrometry method, for the first time. The temperature dependence of the intensities of Li3Cl2 +, Li4Cl3 + and Li5Cl4 + ions were measured in the interval 1128–1616, 1126–1435, and 1947–2278 K, respectively. The following ionization energies were obtained: IE(Li3Cl2) = 4.51 ± 0.2 eV, IE(Li4Cl3) = 4.18 ± 0.2 eV, and IE(Li4Cl3) = 5.05 ± 0.2 eV. A good correlation of the experimental results with the theoretical adiabatic ionization energy is recognized. Results are confirmation that these clusters can be classified as “superalkalis.”